Along with U.S. manufacturing jobs, you can count another victim of global trade: American trees.

The most destructive forest pests from abroad are arriving at an accelerated pace, according to a new study. Between 1990 and 2006, new ones were discovered in the U.S. at an average rate of 1.2 per year, or nearly three times the detection rate during the previous 130 years.

The jump coincides with a rise in imports, leading the authors of a paper published in the December issue of BioScience to conclude that current rules and inspections to keep forest pests out of the country aren't that effective.

"Strengthened regulations to prevent introductions of nonindigenous species... along with enhanced efforts to rapidly detect newly established forest insects and pathogens, are critical to maintaining the health of North American forests and wildlands," wrote the six authors.

Reviewing data on alien pests, the researchers compiled a list of 455 non-native insect species and 16 pathogens that have colonized trees in native forests or urban settings. The first, the codling moth, was recorded in 1635.

Most feast on sap or foliage. Not all of them do that much damage. But as international trade has grown, so has the rate of invasion of the most harmful species.

"Global trade has had tremendous benefits for Americans," lead author Juliann Aukema from the National Center for Ecological Analysis and Synthesis in Santa Barbara said in a news release. "Unfortunately, it also has resulted in the introduction of destructive insects and other organisms that threaten native ecosystems and the services they provide."

Sudden oak death, carried by an exotic pathogen, is killing and sickening West Coast oaks.
Maples in New York have fallen to the Asian longhorned beetle, which probably hopped a ride to the U.S. in wooden packing materials. In the Midwest and Northeast, the emerald ash borer, a native of Asia, is drilling away.

Better screening at the country's airports and ports is needed, the scientists suggested.

"Right now the focus is on finding bombs and weapons," said co-author Betsy Von Holle, an assistant biology professor at the University of Central Florida. "That's absolutely right, but we also need to be more aggressive about biological threats that could undermine large parts of the U.S. economy and harm our environment."

Photo: The Asian longhorned beetle. Credit: U.S. Department of Agriculture